Methods for manufacturing resin structure and micro-structure

ABSTRACT

A resin structure for the formation of a micro-structure is manufactured by (A) applying a composition comprising a polymer, a photoacid generator, an epoxy compound, and an organic solvent onto a substrate, (B) heating the composition to form a sacrificial film, (C) exposing imagewise the film to first high-energy radiation, (D) developing the film in an alkaline developer to form a sacrificial film pattern, (E) exposing the sacrificial film pattern to UV as second high-energy radiation, and (F) heating the substrate at 80-250° C. The exposure dose of first high-energy radiation in step (C) is up to 250 mJ/cm 2 . At the end of step (F), the sacrificial film has a sidewall angle of 80°-90° relative to the substrate.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35U.S.C. §119(a)on Patent Application No. 2013-021433 filed in Japan on Feb. 6, 2013,the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to methods for manufacturing amicro-structure-forming resin structure and a micro-structure, commonlyreferred to as micro-electromechanical system (MEMS) element. Moreparticularly, it relates to a method for manufacturing a micro-structureby a sacrificial layer etching technique including forming a resinstructure having a resin pattern on a substrate, depositing an inorganicmaterial film on the resin structure, optionally processing theinorganic material film into a predetermined shape, and etching away theresin structure to form a structure having a desired space.

BACKGROUND ART

In the manufacture of MEMS elements having mechanical element parts suchas sensors and actuators integrated on substrates, the predominantportion is processed using the semiconductor integrated circuitfabrication technology. For forming movable structure parts andstereo-structure parts, the MEMS technology utilizes inherent processingtechniques such as sacrificial layer etching technique, deepdrilling/etching technique, and anisotropic etching technique. Amongthese techniques, the sacrificial layer etching technique is animportant technique involving depositing a plurality of layers on asubstrate, and selectively removing the lower layer called sacrificiallayer, leaving the upper layer. With respect to the materials used inthe sacrificial layer, many reports have been made. For example, JP-A2000-255072 discloses a positive novolak resist composition which can beadvantageously processed to form fine size features, but has poor heatresistance, by which a choice of the material of the upper layer islimited.

As a solution to this problem, one approach proposed thus far is byproviding a positive resist composition based on a cresol novolak resinand adding a crosslinker thereto, followed by certain steps. Althoughthis approach enables relatively fine size processing and offerssufficient heat resistance, it has poor sensitivity and fails to reach atarget resolution estimated in the future.

CITATION LIST

-   Patent Document 1: JP-A 2000-255072-   Patent Document 2: JP-A 2012-018390

SUMMARY OF INVENTION

In connection with the sacrificial layer etching technique which is apredominant stage of the MEMS device fabrication, an object of theinvention is to provide methods for manufacturing amicro-structure-forming resin structure from an optically patternablefilm-forming composition and a micro-structure, which can form asacrificial film pattern having an optimum pattern profile, highresolution, high sensitivity, and heat resistance sufficient to acceptthe deposition of silicon or metal material at high temperature andhence, can form a high-accuracy micro-structure on the cured film of thecomposition.

The inventors have found that the above and other objects can beattained by using an optically patternable film-forming compositioncomprising a polymer having some phenolic hydroxyl groups protected witha protective group eliminatable by acid, a photoacid generator, and anepoxy compound containing at least two epoxy groups and having amolecular weight of 200 to 3,000, and processing it until amicro-structure-forming resin structure and a micro-structure aremanufactured.

In one aspect, the invention provides a method for manufacturing a resinstructure for the formation of a micro-structure, comprising the stepsof:

(A) applying an optically patternable film-forming composition onto asubstrate, said composition comprising (1) a polymer having somephenolic hydroxyl groups protected with an acid-labile protective group,(2) a photoacid generator, (3) an epoxy compound containing at least twoepoxy groups and having a molecular weight of 200 to 3,000, and (4) anorganic solvent,

(B) heating the composition on the substrate to form an opticallypatternable sacrificial film having a thickness of 1 to 30 μm,

(C) exposing the sacrificial film to first high-energy radiation inaccordance with a pattern layout image,

(D) developing the sacrificial film in an alkaline developer to form asacrificial film pattern,

(E) exposing the sacrificial film pattern to second high-energyradiation which is ultraviolet radiation, and

(F) heating the substrate at 80 to 250° C.,

wherein the exposure dose of first high-energy radiation in step (C) isup to 250 mJ/cm², and

at the end of step (F), the sacrificial film has a sidewall whichmaintains an angle of 80° to 90° relative to the substrate.

In a preferred embodiment, the epoxy compound (3) in the opticallypatternable film-forming composition has a structure of the generalformula (2):

wherein R₁, R₂, R₃ and R₄ are each independently hydrogen, hydroxyl,epoxy, or a monovalent organic group of 1 to 40 carbon atoms which maycontain an epoxy group, or a pair of adjacent R₁ and R₃, R₁ and R₄, R₂and R₃, or R₂ and R₄ may bond together to form an optionallyepoxy-containing ring with the carbon atom to which they are attached,at least two epoxy groups in total being present on at least one groupof R₁ to R₄.

More preferably, the epoxy compound (3) is selected from among abisphenol A epoxy compound, bisphenol E epoxy compound, bisphenol Fepoxy compound, fluorene epoxy compound, dicyclopentadiene epoxycompound, biphenyl epoxy compound, glycidyl ester compound,glycidylamine compound, phenol novolak epoxy resin, cresol novolak epoxyresin, alicyclic epoxy resin, and a mixture thereof.

In a preferred embodiment, the polymer (1) is a resin represented by thegeneral formula (1) and having a weight average molecular weight of1,000 to 500,000.

Herein R¹ is hydrogen, hydroxyl, C₁-C₃ straight or branched alkyl,halogen, or trifluoromethyl, R² is hydroxyl, halogen or trifluoromethyl,R³ is an optionally substituted C₁-C₄ alkyl, ditrifluoromethylhydroxy,or —OR group, R is a C₁-C₂₀ straight, branched or cyclic alkyl,alkoxyalkyl, alkoxycarbonyl or trialkylsilyl group, which may contain aheteroatom, R⁴ is hydrogen, an optionally substituted C₁-C₄ alkyl,ditrifluoromethylhydroxy, or —OR group, R⁵ is hydrogen or methyl, R⁶ ishydrogen, methyl, alkoxycarbonyl, cyano, halogen or trifluoromethyl, R⁷is a C₄-C₃₀ monovalent hydrocarbon group which may contain a heteroatom,n is an integer of 0 to 4, m is an integer of 0 to 5, p, q, r and s eachare 0 or a positive number, q+r is a positive number, and R³ where q isa positive number, R⁴ where r is a positive number, or at least one ofR³ and R⁴ where both q and r are positive numbers is a protective groupin which some phenolic hydroxyl groups are eliminatable by acid,provided that p+q+r+s=1.

In a preferred embodiment, the optically patternable film-formingcomposition further comprises (5) a basic compound.

In a preferred embodiment, the exposure dose of first high-energyradiation in step (C) is up to 150 mJ/cm². Also preferably, the firsthigh-energy radiation in step (C) is ultraviolet radiation having awavelength of 200 to 450 nm.

In a preferred embodiment, the second high-energy radiation in step (E)is ultraviolet radiation having a wavelength of 254 nm or a broad bandof ultraviolet radiation covering 254 nm.

In a preferred embodiment, step (F) includes holding at two or moreholding temperatures, the difference between the lowest holdingtemperature and the highest holding temperature being at least 50° C.More preferably, step (F) includes heating at a first temperature of 80to 150° C. for 20 to 180 minutes and then heating at a temperature of180 to 250° C. which is at least 50° C. higher than the firsttemperature for 20 to 180 minutes.

In a preferred embodiment, the sacrificial film has a sidewall whichmaintains an angle of 85° to 90° relative to the substrate.

In another aspect, the invention provides a method for manufacturing amicro-structure comprising the steps of forming an inorganic materialfilm on the resin structure defined above, and removing the residualsacrificial film to define a space.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the invention, a micro-structure is manufactured using anoptically patternable film-forming composition. The methods areeffective for manufacturing a sacrificial film pattern having heatresistance and for forming a pattern of micro-structure on the curedfilm of the composition at a high sensitivity, independent of the typeof substrate.

DESCRIPTION OF EMBODIMENTS

In the disclosure, the singular forms “a,” “an” and “the” include pluralreferents unless the context clearly dictates otherwise. “Optional” or“optionally” means that the subsequently described event orcircumstances may or may not occur, and that description includesinstances where the event or circumstance occurs and instances where itdoes not. The notation (C_(n)—C_(m)) means a group containing from n tom carbon atoms per group. The abbreviation “MEMS” stands formicro-electromechanical system, “UV” for ultraviolet, “Mw” for weightaverage molecular weight, “GPC” for gel permeation chromatography, and“PAG” for photoacid generator.

The invention pertains to a method for manufacturing a micro-structurewhich may be advantageously used in the fabrication of MEMS componentsby surface micromachining, and a method for manufacturing a resinstructure for forming the micro-structure, using an opticallypatternable film-forming composition.

The resin structure for use in the formation of a micro-structure has asacrificial film pattern formed on a substrate. The sacrificial film isformed of an optically patternable film-forming composition comprisingat least (1) a polymer having some phenolic hydroxyl groups protectedwith a protective group eliminatable by acid (i.e., acid-labileprotective group), (2) a photoacid generator, (3) an epoxy compoundcontaining at least two epoxy groups and having a molecular weight of200 to 3,000, and (4) an organic solvent.

The polymer used herein as component (1) is not particularly limited aslong as it has phenolic hydroxyl groups some of which are protected witha protective group eliminatable by acid (i.e., acid-labile protectivegroup). Preferred is a polymer comprising recurring units of the generalformula (1) and having a weight average molecular weight (Mw) of 1,000to 500,000.

Herein R¹ is hydrogen, hydroxyl, C₁-C₃ straight or branched alkyl,halogen, or trifluoromethyl. R² is hydroxyl, halogen or trifluoromethyl.R³ is an optionally substituted C₁-C₄ alkyl, ditrifluoromethylhydroxy,or —OR group, wherein R is a C₁-C₂₀ straight, branched or cyclic alkyl,alkoxyalkyl, alkoxycarbonyl or trialkylsilyl group, which may contain aheteroatom (e.g., oxygen). R⁴ is hydrogen, an optionally substitutedC₁-C₄ alkyl, ditrifluoromethylhydroxy, or —OR group, wherein R is aC₁-C₂₀ straight, branched or cyclic alkyl, alkoxyalkyl, alkoxycarbonylor trialkylsilyl group, which may contain a heteroatom (e.g., oxygen).R⁵ is hydrogen or methyl. R⁶ is hydrogen, methyl, alkoxycarbonyl, cyano,halogen or trifluoromethyl. R⁷ is a C₄-C₃₀ monovalent hydrocarbon group,typically alkyl, which may contain a heteroatom. The subscript n is aninteger of 0 to 4, m is an integer of 0 to 5, p, q, r and s each are 0or a positive number, q+r is a positive number, provided that p+q+r+s=1.R³ where q is a positive number, R⁴ where r is a positive number, or atleast one of R³ and R⁴ where both q and r are positive numbers is aprotective group (i.e., acid labile group) in which some phenolichydroxyl groups are eliminable by acid.

When R¹, R², and R⁶ each stand for a halogen atom, suitable halogenatoms include fluorine, chlorine and bromine.

When R³ and R⁴ each stand for a straight or branched alkyl group,suitable alkyl groups include methyl, ethyl, propyl, isopropyl, n-butyl,isobutyl, and tert-butyl. When —OR group has an acid labile groupfunction, the —OR group may be selected from a variety of groups, but ispreferably selected from among groups of the following formulae (3) and(4), C₄-C₂₀ straight, branched or cyclic tertiary alkoxy groups,trialkylsiloxy groups in which each alkyl moiety has 1 to 6 carbonatoms, C₄-C₂₀ oxoalkoxy groups, tetrahydropyranyloxy,tetrahydrofuranyloxy and trialkylsiloxy groups.

Herein R⁸, R⁹, R¹⁰, R¹¹, and R¹² are each independently hydrogen or aC₁-C₈ straight or branched alkyl group. R¹⁰ is a C₁-C₁₈, monovalenthydrocarbon group which may be separated by an oxygen atom. A pair of R⁸and R⁹, R⁸ and R¹⁰, or R⁹ and R¹⁰ may bond together to form a ring withthe carbon atom or the carbon and oxygen atoms to which they areattached. In the case of ring formation, each of participant R⁸, R⁹, andR¹⁰ is a C₁-C₁₈ straight or branched alkylene group. R¹³ is a C₄-C₄₀straight, branched or cyclic alkyl group. The subscript “a” is 0 or aninteger of 1 to 4.

Examples of the acid labile group of formula (3) include methoxyethoxy,ethoxyethoxy, n-propoxyethoxy, isopropoxyethoxy, n-butoxyethoxy,isobutoxyethoxy, tert-butoxyethoxy, cyclohexyloxyethoxy, methoxypropoxy,ethoxypropoxy, 1-methoxy-1-methyl-ethoxy, and 1-ethoxy-1-methyl-ethoxy.Examples of the acid labile group of formula (4) includetert-butoxycarbonyloxy, tert-butoxycarbonylmethyloxy,ethylcyclopentylcarbonyloxy, ethylcyclohexylcarbonyloxy, andmethylcyclopentylcarbonyloxy. Suitable trialkylsiloxy groups includethose having C₁-C₆ alkyl, such as trimethylsiloxy.

When the monovalent hydrocarbon group of R⁷ is a monovalent tertiaryhydrocarbon group, typically tertiary alkyl, it may be selected from avariety of such groups, preferably from groups of the general formulae(5) and (6).

Herein R¹⁴ is methyl, ethyl, isopropyl, cyclohexyl, cyclopentyl, vinyl,acetyl, phenyl, benzyl or cyano, and b is an integer of 0 to 3.

Herein R¹⁵ is methyl, ethyl, isopropyl, cyclohexyl, cyclopentyl, vinyl,phenyl, benzyl or cyano.

Of the cyclic alkyl groups of formula (5), 5-membered rings arepreferred. Examples include 1-methylcyclopentyl, 1-ethylcyclopentyl,1-isopropylcyclopentyl, 1-vinylcyclopentyl, 1-acetylcyclopentyl,1-phenylcyclopentyl, 1-cyanocyclopentyl, 1-methylcyclohexyl,1-ethylcyclohexyl, 1-isopropylcyclohexyl, 1-vinylcyclohexyl,1-acetylcyclohexyl, 1-phenylcyclohexyl, and 1-cyanocyclohexyl.

Examples of the group of formula (6) include t-butyl, 1-vinyldimethyl,1-benzyldimethyl, 1-phenyldimethyl, and 1-cyanodimethyl.

Of the recurring units (s), those units shown below are preferred. Thealkyl group to form tertiary ester in these recurring units is alsopreferred as R⁷.

In view of characteristics of the optically patternable film-formingcomposition, n is 0 or an integer of 1 to 4, and m is 0 or an integer of1 to 5. The subscripts p, q, r and s each are 0 or a positive number, atleast either one of p and q is a positive number. The preferred rangesare: 0≦p≦0.8, more preferably 0.3≦p≦0.8, 0≦q≦0.5, 0≦r≦0.5, and 0≦s≦0.35.At least one of q and r is a positive number (i.e., 0<q≦0.5 and/or0<r≦0.5). It is more preferred that 0≦q≦0.3 and 0≦r≦0.3. Also in thiscase, at least one of q and r is a positive number (i.e., 0<q≦0.3 and/or0<r≦0.3). As long as the polymer of formula (1) has a structureessentially comprising units (q) and/or units (r), it offers asignificant contrast of alkali dissolution rate and a high resolution.As long as p is in the range: 0<p≦0.8, the alkali dissolution rate ofthe unexposed region is maintained appropriate, eliminating the risk ofreducing resolution. The size and profile of a pattern can be controlledas desired by selecting the values of p, q, r and s in theabove-described ranges.

Of the polymers comprising units of formula (1), binary polymers (1)-1and (1)-2, ternary polymers (1)-3, (1)-4, (1)-5 and (1)-6, andquaternary polymers (1)-7, all shown below, are preferred. It is notedthat R¹ to R⁷, m and n in the following formulae are as defined above.

(0.5≦p≦0.8, 0.2≦q≦0.5, p+q=1)

(0.5≦p≦0.8, 0.2≦r≦0.5, p+r=1)

(0.4≦p≦0.8, 0<q≦0.5, 0<s 0.3, p+q+s=1)

(0.4≦p≦0.8, 0<r≦0.5, 0<s 0.3, p+r+s=1)

(0.4≦p≦0.8, 0<q≦0.5, 0.1≦r≦0.5, p+q+r=1)

(0<q≦0.5, 0.2≦r<0.5, 0<s≦0.3, q+r+s=1)

(0.3≦p≦0.8, 0<q≦0.5, 0.1≦r≦0.5, 0<s≦0.3, p+q+r+s=1)

It is preferred from the standpoints of resist pattern formation andheat resistance that the polymer have a Mw of 1,000 to 500,000, morepreferably 2,000 to 30,000, as measured by GPC versus polystyrenestandards.

If a multi-component polymer comprising units of formula (1) has a widemolecular weight distribution or dispersity (Mw/Mn), which indicates thepresence of lower and higher molecular weight polymer fractions, thereis a possibility that foreign matter is left on the pattern or thepattern profile is degraded. The influences of molecular weight anddispersity become stronger as the pattern rule becomes finer. Therefore,the multi-component polymer should preferably have a narrow dispersity(Mw/Mn) of 1.0 to 3.0, especially 1.0 to 2.0, in order to provide anoptically patternable film-forming composition suitable formicropatterning to a small feature size.

In the polymer mentioned above, an acid labile group having the generalformula (3) or (4) may be introduced into a phenolic hydroxyl group. Forexample, a polymer having phenolic hydroxyl groups may be reacted with ahalogenated alkyl ether in the presence of a base, obtaining a polymerin which some phenolic hydroxyl groups are protected with alkoxyalkylgroups.

In the polymer, units of a polymerizable monomer having an unsaturatedbond may be copolymerized as long as the invention is not adverselyaffected.

The photoacid generator (PAG) used in the optically patternablefilm-forming composition may be any compound capable of generating anacid upon exposure to high-energy radiation. Suitable PAGs includesulfonium salts, iodonium salts, sulfonyldiazomethane andN-sulfonyloxyimide acid generators. The acid generators may be usedalone or in admixture of two or more.

Sulfonium salts are salts of sulfonium cations with sulfonates.Exemplary sulfonium cations include triphenylsulfonium,(4-tert-butoxyphenyl)diphenylsulfonium,bis(4-tert-butoxyphenyl)phenylsulfonium,tris(4-tert-butoxyphenyl)sulfonium,(3-tert-butoxyphenyl)diphenylsulfonium,bis(3-tert-butoxyphenyl)phenylsulfonium,tris(3-tert-butoxyphenyl)sulfonium,(3,4-di-tert-butoxyphenyl)diphenylsulfonium,bis(3,4-di-tert-butoxyphenyl)phenylsulfonium,tris(3,4-di-tert-butoxyphenyl)sulfonium,diphenyl(4-thiophenoxyphenyl)sulfonium,(4-tert-butoxycarbonylmethyloxyphenyl)diphenylsulfonium,tris(4-tert-butoxycarbonylmethyloxyphenyl)sulfonium,(4-tert-butoxyphenyl)bis(4-dimethylaminophenyl)sulfonium,tris(4-dimethylaminophenyl)sulfonium, 2-naphthyldiphenylsulfonium,dimethyl(2-naphthyl)sulfonium, 4-hydroxyphenyldimethylsulfonium,4-methoxyphenyldimethylsulfonium, trimethylsulfonium,2-oxocyclohexylcyclohexylmethylsulfonium, trinaphthylsulfonium, andtribenzylsulfonium.

Exemplary sulfonates include trifluoromethanesulfonate,nonafluorobutanesulfonate, heptadecafluorooctanesulfonate,2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate,4-(trifluoromethyl)benzenesulfonate, 4-fluorobenzenesulfonate,toluenesulfonate, benzenesulfonate,4-(4-toluenesulfonyloxy)benzenesulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, and methanesulfonate. Sulfonium salts based oncombination of the foregoing examples are included.

Iodonium salts are salts of iodonium cations with sulfonates. Exemplaryiodonium cations include aryliodonium cations such as diphenyliodonium,bis(4-tert-butylphenyl)iodonium, 4-tert-butoxyphenylphenyliodonium, and4-methoxyphenylphenyliodonium. Exemplary sulfonates includetrifluoromethanesulfonate, nonafluorobutanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-(trifluoromethyl)benzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,4-(4-toluenesulfonyloxy)benzenesulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, and methanesulfonate. Iodonium salts based oncombination of the foregoing examples are included.

Exemplary sulfonyldiazomethane compounds include bissulfonyldiazomethanecompounds and sulfonylcarbonyldiazomethane compounds such asbis(ethylsulfonyl)diazomethane, bis(1-methylpropylsulfonyl)diazomethane,bis(2-methylpropylsulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane,bis(perfluoroisopropylsulfonyl)diazomethane,bis(phenylsulfonyl)diazomethane,bis(4-methylphenylsulfonyl)diazomethane,bis(2,4-dimethylphenylsulfonyl)diazomethane,bis(2-naphthylsulfonyl)diazomethane,4-methylphenylsulfonylbenzoyldiazomethane,tert-butylcarbonyl-4-methylphenylsulfonyldiazomethane,2-naphthylsulfonylbenzoyldiazomethane,4-methylphenylsulfonyl-2-naphthoyldiazomethane,methylsulfonylbenzoyldiazomethane, andtert-butoxycarbonyl-4-methylphenylsulfonyldiazomethane.

Suitable N-sulfonyloxyimide PAGs include combinations of imide skeletonswith sulfonates. Exemplary imide skeletons are succinimide, naphthalenedicarboxylic acid imide, phthalimide, cyclohexyldicarboxylic acid imide,5-norbornene-2,3-dicarboxylic acid imide, and7-oxabicyclo-[2.2.1]-5-heptene-2,3-dicarboxylic acid imide. Exemplarysulfonates include trifluoromethanesulfonate, nonafluorobutanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, and methanesulfonate.

Benzoinsulfonate PAGs include benzoin tosylate, benzoin mesylate, andbenzoin butanesulfonate.

Pyrogallol trisulfonate PAGs include pyrogallol, phloroglucinol,catechol, resorcinol, and hydroquinone, in which all hydroxyl groups aresubstituted by trifluoromethanesulfonate, nonafluorobutanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, or methanesulfonate.

Nitrobenzyl sulfonate PAGs include 2,4-dinitrobenzyl sulfonates,2-nitrobenzyl sulfonates, and 2,6-dinitrobenzyl sulfonates, withexemplary sulfonates including trifluoromethanesulfonate,nonafluorobutanesulfonate, heptadecafluorooctanesulfonate,2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate,4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate,toluenesulfonate, benzenesulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, and methanesulfonate. Also useful are analogousnitrobenzyl sulfonate compounds in which the nitro group on the benzylside is substituted by trifluoromethyl.

Sulfone PAGs include bis(phenylsulfonyl)methane,bis(4-methylphenylsulfonyl)methane, bis(2-naphthylsulfonyl)methane,2,2-bis(phenylsulfonyl)propane, 2,2-bis(4-methylphenylsulfonyl)propane,2,2-bis(2-naphthylsulfonyl)propane,2-methyl-2-(p-toluenesulfonyl)propiophenone,2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane, and2,4-dimethyl-2-(p-toluenesulfonyl)pentan-3-one.

Glyoxime derivative PAGs includebis-O-(p-toluenesulfonyl)-α-dimethylglyoxime,bis-O-(p-toluenesulfonyl)-α-diphenylglyoxime,bis-O-(p-toluenesulfonyl)-α-dicyclohexylglyoxime,bis-O-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime,bis-O-(p-toluenesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,bis-O-(n-butanesulfonyl)-α-dimethylglyoxime,bis-O-(n-butanesulfonyl)-α-diphenylglyoxime,bis-O-(n-butanesulfonyl)-α-dicyclohexylglyoxime,bis-O-(n-butanesulfonyl)-2,3-pentanedioneglyoxime,bis-O-(n-butanesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,bis-O-(methanesulfonyl)-α-dimethylglyoxime,bis-O-(trifluoromethanesulfonyl)-α-dimethylglyoxime,bis-O-(1,1,1-trifluoroethanesulfonyl)-α-dimethylglyoxime,bis-O-(tert-butanesulfonyl)-α-dimethylglyoxime,bis-O-(perfluorooctanesulfonyl)-α-dimethylglyoxime,bis-O-(cyclohexylsulfonyl)-α-dimethylglyoxime,bis-O-(benzenesulfonyl)-α-dimethylglyoxime,bis-O-(p-fluorobenzenesulfonyl)-α-dimethylglyoxime,bis-O-(p-tert-butylbenzenesulfonyl)-α-dimethylglyoxime,bis-O-(xylenesulfonyl)-α-dimethylglyoxime, andbis-O-(camphorsulfonyl)-α-dimethylglyoxime.

Although the optimum anion of the generated acid varies with suchfactors as ease of scission of the acid labile group in the polymer, ananion which is non-volatile and not extremely highly diffusive isgenerally selected. Appropriate anions include anions of benzenesulfonicacid, toluenesulfonic acid, 4-(4-toluenesulfonyloxy)benzenesulfonicacid, pentafluorobenzenesulfonic acid, 2,2,2-trifluoroethanesulfonicacid, nonafluorobutanesulfonic acid, heptadecafluorooctanesulfonic acid,and camphorsulfonic acid.

Of the aforementioned PAGs, where the first high-energy radiation is i-or g-line of a mercury lamp, or broadband light, naphthalimidyl andsulfonyloxyimino are preferred. Where the first high-energy radiation isthat from a light source of short wavelength of up to 300 nm, such asKrF excimer laser or mercury 254-nm line, sulfonyloxyimino andbissulfonyldiazomethane are preferred.

An amount of the PAG added is typically 0.05 to 15 parts by weight,preferably 0.1 to 10 parts by weight per 100 parts by weight (as solids)of the polymer or base resin in the optically patternable film-formingcomposition. The PAG may be added alone or in admixture of two or more.The transmittance of the resist film can be controlled by using a PAGhaving a low transmittance at the exposure wavelength and adjusting theamount of the PAG added.

Component (3) used herein is an epoxy compound containing at least twoepoxy groups and having a molecular weight of 200 to 3,000. Included arecompounds containing at least two epoxy groups in a molecule, having thegeneral formula (2).

Herein R₁, R₂, R₃ and R₄ are each independently hydrogen, hydroxyl,epoxy, or a monovalent organic group of 1 to 40 carbon atoms which maybe straight, branched or cyclic and which may contain an epoxy group. Apair of adjacent R₁ and R₃, R₁ and R₄, R₂ and R₃, or R₂ and R₄ may bondtogether to form an optionally epoxy-containing ring with the carbonatom to which they are attached. Suitable monovalent organic groupsinclude monovalent hydrocarbon groups which may be substituted withhalogen atoms such as fluorine, chlorine or bromine and whose methylenemoiety may be substituted by an oxygen atom, carbonyl moiety or thelike. The compound should contain epoxy groups such that the totalnumber of epoxy groups on at least one group of R₁ to R₄ is at least 2.

Suitable epoxy compounds include bisphenol A epoxy compounds, bisphenolE epoxy compounds, bisphenol F epoxy compounds, and fluorene epoxycompounds. Also useful are dicyclopentadiene epoxy compounds, biphenylepoxy compounds, glycidyl ester compounds such as diglycidyl phthalate,diglycidyl hexahydrophthalate, and dimethylglycidiyl phthalate; andglycidylamine compounds such as tetraglycidyldiaminodiphenylmethane,triglycidyl-p-aminophenol, diglycidylaniline, diglycidyltoluidine, andtetraglycidylbisaminomethylcyclohexane. Suitable epoxy resins includephenol novolak epoxy resins, cresol novolak epoxy resins, and alicyclicepoxy resins such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate. These compounds may be used alone or in admixture of two ormore. If desired, a monofunctional epoxy compound containing one epoxygroup in a molecule may be added thereto. Of the foregoing epoxycompounds, preference is given to bisphenol A epoxy compounds, bisphenolE epoxy compounds, bisphenol F epoxy compounds, and fluorene epoxycompounds.

The epoxy compound should have a molecular weight of 200 to 3,000,preferably 300 to 2,000. If the molecular weight is less than 200, thereis a propensity that dark reaction takes place in the exposed region,failing to form the desired pattern profile. If the molecular weightexceeds 3,000, the dissolution rate declines, failing to gain thedesired sensitivity. It is noted that the term “molecular weight”refers, for a simple compound, to a molecular weight calculated from itsstructural formula, and for a mixture or polymer, to a weight averagemolecular weight (Mw) as determined by GPC versus polystyrene standards.

An amount of the epoxy compound added is typically 2 to 30 parts byweight, preferably 3 to 20 parts by weight per 100 parts by weight (assolids) of the polymer or base resin in the optically patternablefilm-forming composition. If the amount of the epoxy compound added isless than 2 parts, the pattern may be susceptible to thermal flow duringthe heating step (F), largely deviating from the pattern profileresulting from step (D). If the amount of the epoxy compound addedexceeds 30 parts, noticeable dark reaction can take place upon lightirradiation of step (C), failing in pattern formation.

Examples of the organic solvent include, but are not limited to, butylacetate, amyl acetate, cyclohexyl acetate, 3-methoxybutyl acetate,methyl ethyl ketone, methyl amyl ketone, cyclohexanone, cyclopentanone,3-ethoxyethyl propionate, 3-ethoxymethyl propionate, 3-methoxymethylpropionate, methyl acetoacetate, ethyl acetoacetate, diacetone alcohol,methyl pyruvate, ethyl pyruvate, propylene glycol monomethyl ether,propylene glycol monoethyl ether, propylene glycol monomethyl etherpropionate, propylene glycol monoethyl ether propionate, ethylene glycolmonomethyl ether, ethylene glycol monoethyl ether, diethylene glycolmonomethyl ether, diethylene glycol monoethyl ether,3-methyl-3-methoxybutanol, N-methylpyrrolidone, dimethyl sulfoxide,γ-butyrolactone, propylene glycol methyl ether acetate (PGMEA),propylene glycol ethyl ether acetate, propylene glycol propyl etheracetate, methyl lactate, ethyl lactate, propyl lactate, andtetramethylene sulfone. Of these, propylene glycol alkyl ether acetatesand alkyl lactates are preferred. The solvents may be used alone or inadmixture of two or more. The preferred solvent mixture is a combinationof a propylene glycol alkyl ether acetate with an alkyl lactate. It isnoted that the alkyl groups of the propylene glycol alkyl ether acetatesare preferably those of 1 to 4 carbon atoms, for example, methyl, ethyl,and propyl, with methyl and ethyl being especially preferred. Since thepropylene glycol alkyl ether acetates include 1,2- and 1,3-substitutedones, each includes three isomers depending on the combination ofsubstituted positions, which may be used alone or in admixture. It isalso noted that the alkyl groups of the alkyl lactates are preferablythose of 1 to 4 carbon atoms, for example, methyl, ethyl and propyl,with methyl and ethyl being especially preferred.

In consideration of an appropriate viscosity to ensure effective coatingand a sufficient solubility to prevent particle and foreign matterformation, the propylene glycol alkyl ether acetate or alkyl lactate,when used as the solvent, preferably accounts for at least 50% by weightof the entire solvent. When a mixture of propylene glycol alkyl etheracetate and alkyl lactate is used as the solvent, the mixture preferablyaccounts for at least 50% by weight of the entire solvent. In thissolvent mixture, it is further preferred that the propylene glycol alkylether acetate is 60 to 95% by weight and the alkyl lactate is 5 to 40%by weight.

In the optically patternable film-forming composition, the solvent ispreferably used in an amount of 300 to 2,000 parts by weight, especially400 to 1,000 parts by weight per 100 parts by weight (as solids) of thepolymer or base resin. The concentration of the resulting composition isnot limited thereto as long as a film can be formed by existing methods.

Any well-known additives may be added to the optically patternablefilm-forming composition, if desired. Suitable additives include basiccompounds, other crosslinkers, surfactants, dyes, dissolution promoters,adhesion improvers, and stabilizers.

A suitable basic compound used in the optically patternable film-formingcomposition is a compound capable of suppressing the rate of diffusionwhen the acid generated by the PAG diffuses within the resist film. Theinclusion of this type of basic compound holds down the rate of aciddiffusion within the resist film, resulting in better resolution. Inaddition, it suppresses changes in sensitivity following exposure, thusreducing substrate and environment dependence, as well as improving theexposure latitude and the pattern profile.

Examples of basic compounds include primary, secondary, and tertiaryaliphatic amines, mixed amines, aromatic amines, heterocyclic amines,carboxyl-bearing nitrogen-containing compounds, sulfonyl-bearingnitrogen-containing compounds, hydroxyl-bearing nitrogen-containingcompounds, hydroxyphenyl-bearing nitrogen-containing compounds,alcoholic nitrogen-containing compounds, amide derivatives, and imidederivatives.

Examples of suitable primary aliphatic amines include ammonia,methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine,isobutylamine, sec-butylamine, tert-butylamine, pentylamine,tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine,heptylamine, octylamine, nonylamine, decylamine, dodecylamine,cetylamine, methylenediamine, ethylenediamine, andtetraethylenepentamine. Examples of suitable secondary aliphatic aminesinclude dimethylamine, diethylamine, di-n-propylamine, diisopropylamine,di-n-butylamine, diisobutylamine, di-sec-butylamine, dipentylamine,dicyclopentylamine, dihexylamine, dicyclohexylamine, diheptylamine,dioctylamine, dinonylamine, didecylamine, didodecylamine, dicetylamine,N,N-dimethylmethylenediamine, N,N-dimethylethylenediamine, andN,N-dimethyltetraethylenepentamine. Examples of suitable tertiaryaliphatic amines include trimethylamine, triethylamine,tri-n-propylamine, triisopropylamine, tri-n-butylamine,triisobutylamine, tri-sec-butylamine, tripentylamine,tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine,trioctylamine, trinonylamine, tridecylamine, tridodecylamine,tricetylamine, N,N,N′,N′-tetramethylmethylenediamine,N,N,N′,N′-tetramethylethylenediamine, andN,N,N′,N′-tetramethyltetraethylenepentamine.

Examples of suitable mixed amines include dimethylethylamine,methylethylpropylamine, benzyl amine, phenethylamine, andbenzyldimethylamine. Examples of suitable aromatic and heterocyclicamines include aniline derivatives (e.g., aniline, N-methylaniline,N-ethylaniline, N-propylaniline, N,N-dimethylaniline, 2-methylaniline,3-methylaniline, 4-methylaniline, ethylaniline, propylaniline,trimethylaniline, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline,2,4-dinitroaniline, 2,6-dinitroaniline, 3,5-dinitroaniline, andN,N-dimethyltoluidine), diphenyl(p-tolyl)amine, methyldiphenylamine,triphenylamine, phenylenediamine, naphthylamine, diaminonaphthalene,pyrrole derivatives (e.g., pyrrole, 2H-pyrrole, 1-methylpyrrole,2,4-dimethylpyrrole, 2,5-dimethylpyrrole, and N-methylpyrrole), oxazolederivatives (e.g., oxazole and isooxazole), thiazole derivatives (e.g.,thiazole and isothiazole), imidazole derivatives (e.g., imidazole,4-methylimidazole, and 4-methyl-2-phenylimidazole), pyrazolederivatives, furazan derivatives, pyrroline derivatives (e.g., pyrrolineand 2-methyl-1-pyrroline), pyrrolidine derivatives (e.g., pyrrolidine,N-methylpyrrolidine, pyrrolidinone, and N-methylpyrrolidone),imidazoline derivatives, imidazolidine derivatives, pyridine derivatives(e.g., pyridine, methylpyridine, ethylpyridine, propylpyridine,butylpyridine, 4-(1-butylpentyl)pyridine, dimethylpyridine,trimethylpyridine, triethylpyridine, phenylpyridine,3-methyl-2-phenylpyridine, 4-tert-butylpyridine, diphenylpyridine,benzylpyridine, methoxypyridine, butoxypyridine, dimethoxypyridine,1-methyl-2-pyridine, 4-pyrrolidinopyridine, 1-methyl-4-phenylpyridine,2-(1-ethylpropyl)pyridine, aminopyridine, and dimethylaminopyridine),pyridazine derivatives, pyrimidine derivatives, pyrazine derivatives,pyrazoline derivatives, pyrazolidine derivatives, piperidinederivatives, piperazine derivatives, morpholine derivatives, indolederivatives, isoindole derivatives, 1H-indazole derivatives, indolinederivatives, quinoline derivatives (e.g., quinoline and3-quinolinecarbonitrile), isoquinoline derivatives, cinnolinederivatives, quinazoline derivatives, quinoxaline derivatives,phthalazine derivatives, purine derivatives, pteridine derivatives,carbazole derivatives, phenanthridine derivatives, acridine derivatives,phenazine derivatives, 1,10-phenanthroline derivatives, adeninederivatives, adenosine derivatives, guanine derivatives, guanosinederivatives, uracil derivatives, and uridine derivatives.

Examples of suitable nitrogen-containing compounds with carboxyl includeaminobenzoic acid, indolecarboxylic acid, and amino acid derivatives(e.g. nicotinic acid, alanine, alginine, aspartic acid, glutamic acid,glycine, histidine, isoleucine, glycylleucine, leucine, methionine,phenylalanine, threonine, lysine, 3-aminopyrazine-2-carboxylic acid, andmethoxyalanine). Examples of suitable nitrogen-containing compounds withsulfonyl include 3-pyridinesulfonic acid and pyridiniump-toluenesulfonate. Examples of suitable nitrogen-containing compoundswith hydroxyl, nitrogen-containing compounds with hydroxyphenyl, andalcoholic nitrogen-containing compounds include 2-hydroxypyridine,aminocresol, 2,4-quinolinediol, 3-indolemethanol hydrate,monoethanolamine, diethanolamine, triethanolamine,N-ethyldiethanolamine, N,N-diethylethanolamine, triisopropanolamine,2,2′-iminodiethanol, 2-aminoethanol, 3-amino-1-propanol,4-amino-1-butanol, 4-(2-hydroxyethyl)morpholine,2-(2-hydroxyethyl)pyridine, 1-(2-hydroxyethyl)piperazine,1-[2-(2-hydroxyethoxy)ethyl]piperazine, piperidine ethanol,1-(2-hydroxyethyl)pyrrolidine, 1-(2-hydroxyethyl)-2-pyrrolidinone,3-piperidino-1,2-propanediol, 3-pyrrolidino-1,2-propanediol,8-hydroxyjulolidine, 3-quinuclidinol, 3-tropanol, 1-methyl-2-pyrrolidineethanol, 1-aziridine ethanol, N-(2-hydroxyethyl)phthalimide, andN-(2-hydroxyethyl)isonicotinamide. Examples of suitable amidederivatives include formamide, N-methylformamide, N,N-dimethylformamide,acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, andbenzamide. Suitable imide derivatives include phthalimide, succinimide,and maleimide.

In addition, basic compounds of the following general formula (8) mayalso be added alone or in admixture.

N(X)_(n)(Y)_(3-n)  (8)

Herein, n is equal to 1, 2 or 3; side chain Y is independently hydrogenor a C₁-C₂₀ straight, branched or cyclic alkyl group which may contain ahydroxyl or ether moiety; and side chain X is independently selectedfrom groups of the following general formulas (9) to (11), and X's orY's may bond together to form a ring.

In the formulas, R³⁰⁰, R³⁰² and R³⁰⁵ are each independently a C₁-C₄straight or branched alkylene group. R³⁰¹ and R³⁰⁴ are independentlyhydrogen or a C₁-C₂₀ straight, branched or cyclic alkyl group which maycontain at least one hydroxyl, ether, ester moiety or lactone ring. R³⁰³is a single bond or a C₁-C₄ straight or branched alkylene group. R³⁰⁶ isa C₁-C₂₀ straight, branched or cyclic alkyl group which may contain atleast one hydroxyl, ether, ester moiety or lactone ring.

Illustrative examples of the compounds of formula (8) includetris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine,tris{2-(2-methoxyethoxymethoxy)ethyl}amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)ethyl}amine,tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine,4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane,4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane,1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane, 1-aza-12-crown-4,1-aza-15-crown-5, 1-aza-18-crown-6, tris(2-formyloxyethyl)amine,tris(2-acetoxyethyl)amine, tris(2-propionyloxyethyl)amine,tris(2-butyryloxyethyl)amine, tris(2-isobutyryloxyethyl)amine,tris(2-valeryloxyethyl)amine, tris(2-pivaloyloxyethyl)amine,N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine,tris(2-methoxycarbonyloxyethyl)amine,tris(2-tert-butoxycarbonyloxyethyl)amine,tris[2-(2-oxopropoxy)ethyl]amine,tris[2-(methoxycarbonylmethyl)oxyethyl]amine,tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine,tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]amine,tris(2-methoxycarbonylethyl)amine, tris(2-ethoxycarbonylethyl)amine,N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine,N,N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)-ethylamine,N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)-ethylamine,N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxy-carbonyl]ethylamine,N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxy-carbonyl]ethylamine,N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)-ethylamine,N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)-ethylamine,N,N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylamine,N-(2-hydroxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-hydroxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(3-hydroxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(3-acetoxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-methoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(2-methoxyethoxycarbonyl)ethyl]amine,N-methyl-bis(2-acetoxyethyl)amine, N-ethyl-bis(2-acetoxyethyl)amine,N-methyl-bis(2-pivaloyloxyethyl)amine,N-ethyl-bis[2-(methoxycarbonyloxy)ethyl]amine,N-ethyl-bis[2-(tert-butoxycarbonyloxy)ethyl]amine,tris(methoxycarbonylmethyl)amine, tris(ethoxycarbonylmethyl)amine,N-butyl-bis(methoxycarbonylmethyl)amine,N-hexyl-bis(methoxycarbonylmethyl)amine, andβ-(diethylamino)-δ-valerolactone.

To the optically patternable film-forming composition, the basiccompound may be added alone or in admixture of two or more. From thestandpoint of high sensitivity, the basic compound is preferably addedin an amount of 0 to 2 parts, and especially 0.01 to 1 part by weightper 100 parts by weight (as solids) of the polymer or base resin.

Illustrative, non-limiting examples of the surfactant include nonionicsurfactants, for example, polyoxyethylene alkyl ethers such aspolyoxyethylene lauryl ether, polyoxyethylene stearyl ether,polyoxyethylene cetyl ether, and polyoxyethylene oleyl ether,polyoxyethylene alkylaryl ethers such as polyoxyethylene octylphenolether and polyoxyethylene nonylphenol ether, polyoxyethylenepolyoxypropylene block copolymers, sorbitan fatty acid esters such assorbitan monolaurate, sorbitan monopalmitate, and sorbitan monostearate,and polyoxyethylene sorbitan fatty acid esters such as polyoxyethylenesorbitan monolaurate, polyoxyethylene sorbitan monopalmitate,polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitantrioleate, and polyoxyethylene sorbitan tristearate; fluorochemicalsurfactants such as EFTOP EF301, EF303 and EF352 (Mitsubishi MaterialsElectronic Chemicals Co., Ltd.), Megaface F171, F172 and F173 (DICCorp.), Fluorad FC-430 and FC-431, (Sumitomo 3M Co., Ltd.), AsahiguardAG710, Surflon S-381, S-382, SC101, SC102, SC103, SC104, SC105, SC106,Surfynol E1004, KH-10, KH-20, KH-30 and KH-40 (Asahi Glass Co., Ltd.);organosiloxane polymers KP341, X-70-092 and X-70-093 (Shin-Etsu ChemicalCo., Ltd.), acrylic acid or methacrylic acid Polyflow No. 75 and No. 95(Kyoeisha Ushi Kagaku Kogyo Co., Ltd.). The surfactants may be usedalone or in admixture.

In the optically patternable film-forming composition, the surfactant ispreferably added in an amount of up to 2 parts, and especially up to 1part by weight, per 100 parts by weight (as solids) of the base resin.

Other suitable additives include dissolution promoters as exemplified inJP-A 2011-095662 and azo compounds as exemplified in JP-A 2011-227416,but are not limited thereto.

Described below is the method for manufacturing a resin structure forthe formation of a micro-structure according to the invention. Themethod involves the steps of:

(A) applying the optically patternable film-forming composition onto asubstrate,

(B) heating the composition on the substrate to form an opticallypatternable sacrificial film,

(C) exposing the sacrificial film to first high-energy radiation inaccordance with a pattern layout image,

(D) developing the sacrificial film in an alkaline developer to form asacrificial film pattern,

(E) exposing the sacrificial film pattern to second high-energyradiation which is ultraviolet radiation, and

(F) heating the pattern-bearing substrate at a temperature of 80 to 250°C., thereby yielding a resin structure.

Subsequent to step (F), the process may further involve the steps of:

(G) coating an inorganic material on the sacrificial film pattern toform an inorganic material film,

(H) providing a portion of the inorganic material film with an aperturepenetrating to the sacrificial film pattern, and

(I) etching away the sacrificial film pattern through the aperture,thereby yielding a micro-structure having a space having the contour ofthe sacrificial film pattern.

Step (A) is to apply the optically patternable film-forming compositionas formulated above onto a substrate to form an optically patternablesacrificial film thereon. The film may be formed by many well-knowntechniques.

Typically, a solution containing the positive resist composition may beapplied onto a given substrate by a spin coating, spray coating,printing or other suitable technique.

Examples of the substrate used herein include substrates of Si, SiO₂,SiN, SiON, TiN, WSi, BPSG, SOG and the like, metal substrates such asAu, Ti, W, Cu, Ni—Fe, Ta, Zn, Co and Pb, organic antireflectivecoatings, and cured resist films. The invention is applicable even towafers with a diameter of 100 mm or greater and large-size substratesfor liquid crystal.

The sacrificial film has a thickness of 1 to 30 μm, preferably 2 to 20μm, and more preferably 3 to 10 μm.

In step (B) after coating, heat treatment is carried out at atemperature of about 80 to 140° C. using a hot plate or oven, yieldingan optically patternable sacrificial film having a thickness of 1 to 30μm which is necessary to define a cavity or space in themicro-structure. At a temperature below 80° C., the solvent may be leftin the film. A temperature above 140° C. may invite an extreme drop ofsensitivity and cause certain PAGs to be decomposed. Heat treatment timeis typically 1 minute to 2 hours.

Step (C) is to expose patternwise the optically patternable sacrificialfilm to first high-energy radiation to invite a change of solubility sothat the unnecessary portion of the sacrificial film resulting from step(A) may be dissolved away in the subsequent step or development. Thefirst high-energy radiation used in this patternwise exposure is notparticularly limited as long as the PAG is sensitive thereto. Thepreferred high-energy radiation is UV radiation in the wavelength rangeof 200 to 450 nm. The optimum exposure dose is determined depending on aparticular sacrificial film used. After an optimum exposure dosenecessary for pattern formation is previously determined, the film isexposed to a pattern of radiation in the optimum dose. If the exposuredose exceeds 250 mJ/cm², a practically acceptable irradiation time isnot obtainable in the mass-scale production process due to a throughputspeed delay. Therefore the exposure dose should be up to 250 mJ/cm²,preferably up to 150 mJ/cm², more preferably up to 100 mJ/cm², and alsodesirably at least 10 mJ/cm².

Step (D) is to develop the sacrificial film in an alkaline developer toform a positive sacrificial film pattern. Specifically, the portion ofthe sacrificial film which has been exposed to high-energy radiation instep (C) is dissolved away using an aqueous alkaline developer. Theaqueous alkaline developer is typically an aqueous solution oftetramethylammonium hydroxide (TMAH) in a concentration of 1.0 to 3.5%by weight, preferably 1.3 to 3.0% by weight. Through this development,the portion of the resin film which has been exposed to UV radiation isdissolved away, leaving the desired sacrificial film pattern. Theaqueous alkaline developer used herein is not limited to the organicdeveloper described just above. It is not prohibited to use an inorganicdeveloper based on KOH, for example, as long as the desired developmentrate is achievable. In this sense, any aqueous alkaline developer may beused.

At the end of step (D), the sacrificial film pattern has a sidewallwhich extends at an angle between 80° and 90°, preferably between 85°and 90° relative to the substrate because otherwise the sidewall angleof the film will be reduced in the subsequent heating step, failing toachieve the desired effects.

Step (E) is intended to provide the sacrificial film pattern with heatresistance. To this end, step (E) includes exposing the sacrificial filmpattern to second high-energy radiation which is UV radiation covering awavelength of 254 nm. In one embodiment of step (E), the sacrificialfilm pattern may be exposed to UV radiation covering a wavelength of 254nm while heating at a temperature in the range of 20 to 250° C.,preferably 30 to 220° C. The desired effects may not be fully achievedat a temperature below 20° C. At a temperature in excess of 250° C., thepattern may flow before it is fully cured by crosslinking.

The second high-energy radiation is UV radiation. Upon exposure to UV,the PAG generates an acid, forming crosslinks with sites where theprotective group is removed from the protective group-protected phenolichydroxyl group and/or sites of phenolic hydroxyl groups.

The irradiation of second high-energy radiation may be flood exposureover the entire substrate. Therefore, the second high-energy radiationmay be either single UV having a wavelength of 254 nm or a broad band ofUV covering a wavelength of 254 nm (200 to 600 nm). Crosslink formationmay be facilitated by heating the substrate at a temperature in therange of 20 to 250° C. during the exposure. The heating may be singlestage heating or multi-stage heating. Although the exposure dose ofsecond high-energy radiation is not particularly limited, the exposuredose for effective crosslink formation preferably corresponds to anenergy amount which is 1 to 5,000 times, more preferably 5 to 1,000times, and even more preferably 10 to 500 times the energy amount usedin the exposure to first high-energy radiation.

Step (F) is heat treatment at a temperature of 80 to 250° C., whichintends to promote crosslinking reaction. In the heating step followingthe high-energy radiation irradiation, a heating device such as a hotplate or oven is typically used, although the heating means is notparticularly limited. The heat treatment may be at a single stage ormultiple stages as long as the temperature is within the above range. Ina preferred embodiment, the heat treatment includes holding at two ormore holding temperatures, and the difference between the lowest holdingtemperature and the highest holding temperature is at least 50° C.,because the pattern profile is maintained under such heating conditions.Heat treatment at a temperature below 80° C. is undesirable becausecrosslinking does not fully take place, failing to gain the desiredsacrificial film function. Heat treatment at a temperature in excess of250° C. is undesirable because such high temperature may causeoutgassing.

In a preferred embodiment of step (F), the sacrificial film pattern onthe substrate is heat treated at a first temperature of 80 to 150° C.for 20 to 180 minutes, especially at 100 to 150° C. for 30 to 90minutes, and then heat treated at a second temperature of 180 to 250° C.for 20 to 180 minutes, especially at 180 to 230° C. for 30 to 90minutes, provided that the second temperature is higher than the firsttemperature by at least 50° C.

Since the crosslinking with the aid of PAG during film formation ensuresefficient introduction of crosslinks, high heat resistance is morereadily established. Then a resin structure is readily obtained suchthat even when the sacrificial film pattern resulting from step (F)wherein the structure has a sidewall angle between 80° and 90°,preferably between 85° and 90° is exposed to heat of 200° C., forexample, it experiences a minimized profile change.

Once the sacrificial film pattern is formed as described above, it isoverlaid with an inorganic material film in step (G). Examples of theinorganic material film include amorphous silicon film and silicon oxidefilm. The method for forming the inorganic material film may be physicalvapor deposition (PVD), typically sputtering or chemical vapordeposition (CVD). In particular, the CVD of amorphous silicon ispreferred because a uniform inorganic material film can be easilyformed. Since the CVD technique has a propensity that the temperature ofthe substrate surface rises above 200° C., the invention is advantageousunder such circumstances. The inorganic material film preferably has athickness of 0.1 to 3 μm, more preferably 0.3 to 1 μm, although the filmthickness varies depending on the intended device.

Typically, the inorganic material film deposited on the sacrificial filmpattern which maintains its profile at a high accuracy is thenadditionally processed or shaped, depending on a particular purpose. Instep (H), the inorganic material film is partially provided withapertures for etching away the sacrificial film pattern. The method forforming apertures may be selected as appropriate depending on thefunction and shape of the intended device. The apertures may be formedby any well-known techniques, for example, a lithography process using aphotoresist composition to form apertures or through-holes, and peelingof top surface by chemical mechanical polishing (CMP).

In the subsequent step (I), the sacrificial film pattern is etched awaythrough the apertures by standard ashing techniques such as RF plasmaashing, completing a space having the contour of the sacrificial filmpattern, i.e., yielding a micro-structure.

EXAMPLE

Examples and Comparative Examples are given below for furtherillustrating the invention although the invention is not limitedthereto. Note that Mw is a weight average molecular weight as measuredby GPC versus polystyrene standards, and Mw/Mn is a dispersity ormolecular weight distribution. All parts (pbw) are by weight.

Examples 1 to 7

A resist solution was prepared by dissolving a base resin havingrecurring units shown below (Polymer 1, 2), a photoacid generator(PAG-1), an epoxy compound (CL-1, CL-2, CL-3), a basic compound (Amine1), and a surfactant (X-70-093 by Shin-Etsu Chemical Co., Ltd.) inpropylene glycol monomethyl ether acetate (PGMEA) in accordance with theformulation of Table 1, and filtering through a membrane filter with apore size of 0.5 μm. The resist solution was spin coated onto a siliconsubstrate having a diameter of 200 mm (Step (A)), and soft-baked on ahot plate at 110° C. for 120 seconds to form a resist film of 4.0 μmthick (Step (B)).

Using an i-line stepper NSR-2205i11D (Nikon Corp., NA=0.5), the resistfilm was exposed to radiation of 365 nm in the dose shown in Table 2(Step (C)). The resist film was twice developed in a 2.38 wt % aqueoussolution of tetramethylammonium hydroxide (TMAH) for 50 seconds (Step(D)), forming a line-and-space pattern. Using a scanning electronmicroscope S-4100 (Hitachi High-Technologies Corp.), a cross-sectionalprofile of the resist pattern was observed. Sensitivity is the dosewhich gives an equal width of 4 μm to lines and spaces. A sidewall anglewas measured. The observed profile of pattern on the silicon substrateis also reported in Table 2.

The pattern-bearing substrate was exposed to UV covering 254 nm from UVcure system UMA-802-HC551 (Ushio Inc.) in a dose of 7,500 mJ/cm² (Step(E)) and then heat treated in an oven at 220° C. for one hour (Step(F)). Using SEM S-4100, cross-sectional profiles of the resist patternon the silicon substrate and the cured resist substrate were observed.It is noted that the cured resist substrate is the substrate obtained bycoating the same composition onto a 200-mm silicon substrate to form afilm of 4.0 μm thick, developing the film without exposure, curing thefilm in the cure system, and heat treating in the oven at 220° C. for 1hour (i.e., the same process as above, but exposure omitted).

The substrate was subjected to heat treatment at 250° C. for 30 minutes(Step (G)), which was a simulation of formation of an inorganic materialfilm by plasma-enhanced CVD. After the heat treatment, the filmthickness was measured by an optical interference film thicknessmeasurement system M-6100 (Nanometrics Inc.). Both the film thicknessand the pattern sidewall angle remained unchanged before and after theheat treatment.

On the pattern-bearing wafer following the heat treatment, amorphoussilicon was deposited. Using a plasma-enhanced CVD system (PD-220 bySamuco Co.), an amorphous silicon film of 0.4 μm thick was deposited onthe L/S pattern-bearing substrate by heat treatment at 250° C. for 30minutes. The pattern sidewall was observed for defects under SEM S-4100.

Further, an i-line exposure positive resist composition based on acommon cresol novolak resin (SIPR-9740 by Shin-Etsu Chemical Co., Ltd.)was coated onto the amorphous silicon film on the sacrificial filmpattern to form a photoresist film of 2 μm thick, which was patterned.Using the photoresist pattern as mask, fluorine plasma etching with SF,was carried out, whereby apertures penetrating to the sacrificial filmpattern were defined in the amorphous silicon film. Thereafter, thepattern of resist SIPR-9740 was dissolved away in acetone. This wassubjected to ashing with oxygen plasma by the RF plasma process for 10minutes, forming spaces in the structure. The surface state of thestructure was observed under SEM S-4100.

TABLE 1 Components Example (pbw) 1 2 3 4 5 6 7 Base resin Polym-1Polym-1 Polym-1 Polym-2 Polym-2 Polym-2 Polym-2 (100) (100) (100) (100)(100) (100) (100) PAG PAG-1 PAG-1 PAG-1 PAG-1 PAG-1 PAG-1 PAG-1    (0.7)   (0.7)    (0.7)    (0.7)    (0.7)    (0.7)    (0.7) Epoxy compoundCL-1 CL-3 CL-3 CL-1 CL-1 CL-2 CL-2  (10)  (5)  (15)  (5)  (15)  (10) (20) Basic compound Amine-1 Amine-1 Amine-1 Amine-1 Amine-1 Amine-1Amine-1    (0.10)    (0.25)    (0.08)    (0.20)    (0.10)    (0.14)   (0.06) Surfactant    0.10    0.10    0.10    0.10    0.10    0.10   0.10 Solvent 280 280 280 280 280 280 280

TABLE 2 Example 1 2 3 4 5 6 7 Dose (mJ/cm²) 70 190  50 180  50 80 3010-μm L/S 89 89 89 90 89 90 90 sidewall angle (°) after development10-μm L/S 85 86 83 86 84 84 83 sidewall angle (°) after step (F), oven(220° C.) treatment 10-μm L/S 85 85 83 85 84 83 83 sidewall angle (°)after step (G), oven (250° C.) treatment Pattern on rectangularrectangular rectangular rectangular rectangular rectangular rectangularSi substrate Pattern on rectangular rectangular rectangular rectangularrectangular rectangular rectangular cured resist substrate Defects in nodefects no defects no defects no defects no defects no defects nodefects amorphous silicon film Film removal good good good good goodgood good

The data demonstrate that the sacrificial film pattern formed by theinventive method has adequate properties for surface micromachining ofan inorganic material film or the like by the sacrificial layer etchingtechnique.

Comparative Examples 1 to 8

Comparative Examples 1 to 3 were the same as Examples 1 to 3 except thatdevelopment was followed directly (i.e., without UV cure) by ovenheating. The profile was observed under SEM S-4100. Comparative Examples1 to 3 had a sidewall angle of not more than 70° and failed to form asatisfactory pattern profile.

TABLE 3 Comparative Example 1 2 3 10-μm L/S sidewall angle (°) afterstep (G), 70 67 69 oven (250° C.) treatment

Comparative Examples 4 to 8 used the same resist composition as Example1 except that epoxy-free crosslinkers CL-4 to CL-7, identified below,were added, or no crosslinker was added, as shown in Table 4.

TABLE 4 Components Comparative Example (pbw) 4 5 6 7 8 Base resinPolym-1 Polym-1 Polym-1 Polym-1 Polym-1 (100) (100) (100) (100) (100)PAG PAG-1 PAG-1 PAG-1 PAG-1 PAG-1  (0.7)  (0.7)  (0.7)  (0.7)  (0.7)Crosslinker CL-4 CL-5 CL-6 none CL-7  (5)  (10)  (10)    (10) BasicAmine-1 Amine-1 Amine-1 Amine-1 Amine-1 compound  (0.08)  (0.08)  (0.08) (0.08)  (0.08) Surfactant   0.10   0.10   0.10   0.10   0.10 Solvent 280  280  280  280  280

For Comparative Examples 4 to 8, the same pattern evaluation as inExamples was conducted on the silicon substrate and on the cured resistsubstrate, with the results shown in Table 5.

TABLE 5 Comparative Example Substrate 4 5 6 7 8 Dose (mJ/cm²) — 40 45110 — Pattern on unresolved rectangular rectangular rectangularunresolved Si substrate 10-μm L/S 0 88 89  89 0 sidewall angle (°) afterdevelopment, on Si substrate Pattern on unresolved unresolved footingunresolved unresolved cured resist substrate

Examples 8 to 10

The procedure was the same as in Example 1 except that the conditions ofoven curing (Step (F)) after UV curing in the UV cure system (UshioInc.) were changed as shown in Table 6. The sidewall profile wasobserved. Further, heat treatment was carried out in an oven at 250° C.for 30 minutes (Step (G)), after which the sidewall angle was measured.

TABLE 6 Example 8 9 10 Conditions of Step (F) 100° C./60 min + 150°C./60 min + 85° C./90 min + 220° C./60 min 220° C./60 min 180° C./60 minPattern on Si substrate rectangular rectangular rectangular Pattern oncured resist rectangular rectangular rectangular substrate 10-μm L/Ssidewall angle (°) 86 87 86 after step (F) 10-μm L/S sidewall angle (°)86 87 84 after step (G), oven (250° C.) treatment Defects in amorphoussilicon no defects no defects no defects film Film removal good goodgood

Japanese Patent Application No. 2013-021433 is incorporated herein byreference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. A method for manufacturing a resin structure for the formation of amicro-structure, comprising the steps of: (A) applying an opticallypatternable film-forming composition onto a substrate, said compositioncomprising (1) a polymer having some phenolic hydroxyl groups protectedwith an acid-labile protective group, (2) a photoacid generator, (3) anepoxy compound containing at least two epoxy groups and having amolecular weight of 200 to 3,000, and (4) an organic solvent, (B)heating the composition on the substrate to form an opticallypatternable sacrificial film having a thickness of 1 to 30 μm, (C)exposing the sacrificial film to first high-energy radiation inaccordance with a pattern layout image, (D) developing the sacrificialfilm in an alkaline developer to form a sacrificial film pattern, (E)exposing the sacrificial film pattern to second high-energy radiationwhich is ultraviolet radiation, and (F) heating the substrate at 80 to250° C., wherein the exposure dose of first high-energy radiation instep (C) is up to 250 mJ/cm², and at the end of step (F), thesacrificial film has a sidewall which maintains an angle of 80° to 90°relative to the substrate.
 2. The method of claim 1 wherein the exposuredose of first high-energy radiation in step (C) is up to 150 mJ/cm². 3.The method of claim 1 wherein the epoxy compound (3) in the opticallypatternable film-forming composition has a structure of the generalformula (2):

wherein R₁, R₂, R₃ and R₄ are each independently hydrogen, hydroxyl,epoxy, or a monovalent organic group of 1 to 40 carbon atoms which maycontain an epoxy group, or a pair of adjacent R₁ and R₃, R₁ and R₄, R₂and R₃, or R₂ and R₄ may bond together to form an optionallyepoxy-containing ring with the carbon atom to which they are attached,at least two epoxy groups in total being present on at least one groupof R₁ to R₄.
 4. The method of claim 1 wherein the epoxy compound (3) isat least one compound selected from the group consisting of a bisphenolA epoxy compound, bisphenol E epoxy compound, bisphenol F epoxycompound, fluorene epoxy compound, dicyclopentadiene epoxy compound,biphenyl epoxy compound, glycidyl ester compound, glycidylaminecompound, phenol novolak epoxy resin, cresol novolak epoxy resin, andalicyclic epoxy resin.
 5. The method of claim 1 wherein the polymer (1)is a resin represented by the general formula (1) and having a weightaverage molecular weight of 1,000 to 500,000,

wherein R¹ is hydrogen, hydroxyl, C₁-C₃ straight or branched alkyl,halogen, or trifluoromethyl, R² is hydroxyl, halogen or trifluoromethyl,R³ is an optionally substituted C₁-C₄ alkyl, ditrifluoromethylhydroxy,or —OR group, R is a C₁-C₂₀ straight, branched or cyclic alkyl,alkoxyalkyl, alkoxycarbonyl or trialkylsilyl group, which may contain aheteroatom, R⁴ is hydrogen, an optionally substituted C₁-C₄ alkyl,ditrifluoromethylhydroxy, or —OR group, R⁵ is hydrogen or methyl, R⁶ ishydrogen, methyl, alkoxycarbonyl, cyano, halogen or trifluoromethyl, R⁷is a C₄-C₃₀ monovalent hydrocarbon group which may contain a heteroatom,n is an integer of 0 to 4, m is an integer of 0 to 5, p, q, r and s eachare 0 or a positive number, q+r is a positive number, and R³ where q isa positive number, R⁴ where r is a positive number, or at least one ofR³ and R⁴ where both q and r are positive numbers is a protective groupin which some phenolic hydroxyl groups are eliminatable by acid,provided that p+q+r+s=1.
 6. The method of claim 1 wherein the opticallypatternable film-forming composition further comprises (5) a basiccompound.
 7. The method of claim 1 wherein the first high-energyradiation in step (C) is ultraviolet radiation having a wavelength of200 to 450 nm.
 8. The method of claim 1 wherein the second high-energyradiation in step (E) is ultraviolet radiation having a wavelength of254 nm or a broad band of ultraviolet radiation covering 254 nm.
 9. Themethod of claim 1 wherein step (F) includes holding at two or moreholding temperatures, the difference between the lowest holdingtemperature and the highest holding temperature being at least 50° C.10. The method of claim 9 wherein step (F) includes heating at a firsttemperature of 80 to 150° C. for 20 to 180 minutes and then heating at atemperature of 180 to 250° C. which is at least 50° C. higher than thefirst temperature for 20 to 180 minutes.
 11. The method of claim 1wherein the sacrificial film has a sidewall which maintains an angle of85° to 90° relative to the substrate.
 12. A method for manufacturing amicro-structure comprising the steps of forming an inorganic materialfilm on the resin structure of claim 1 and removing the residualsacrificial film to define a space.